As a technique for controlling localization of a sound image using speakers, VBAP (Vector Base Amplitude Panning) has been known (see Non-Patent Document 1, for example).
By VBAP, a target localization position of a sound image is expressed by a linear sum of vectors extending toward two or three speakers located around the localization position. The coefficients by which the respective vectors are multiplied in the linear sum are used as the gains of the sounds to be output from the respective speakers, and gain adjustment is performed so that a sound image is fixed at the target position.